In a fourth-generation mobile communication Long Term Evolution (LTE) system, a Reference Signal (RS) is a pilot signal known to a receiving end, facilitating the receiving end to implement channel estimation and relevant measurement. The RS plays a very import role in demodulation of receiving signals, elimination of interference, improvement of a Signal Interference Noise Ratio (SINR), cell reselection and handover of a User Equipment (UE, also referred to as terminal) and the like.
There are many types of RSs in LTE. A CRS transmitted to a UE from an Evolved NodeB (eNB) of LTE is a common RS, which is continuously broadcasted in a cell to facilitate all UEs in the cell to estimate and measure quality of a downlink channel of the cell.
Compared with in third-generation mobile communications, a single cell can obtain a higher spectrum efficiency in LTE. However, in a co-channel network consisting of multiple cells contiguously, inter-cell interference is very serious, which significantly reduces the spectrum efficiency. Therefore, LTE put forwards Inter Cell Interference Coordination (ICIC) technology, as shown in FIG. 1. A cell is divided into a cell central area and a marginal area (a white area represents a central area, and an area with a textured pattern represents a marginal area; in some ICIC schemes, a cell is also divided into three areas, i.e., an inner circle, a middle circle and an outer circle). FIG. 1 shows 7 cells (i.e., cell 1 to cell 7), in which cell 1 and each of the other 6 cells (i.e., cell 2 to cell 7) are adjacent to each other. A UE in the central area of a cell can use total transmission resources, while a UE in the marginal area (i.e., a switching area connecting a neighbour cell) of the cell can only use a part of transmission resources. Moreover, resources used by UEs in marginal areas of adjacent cells are different, that is, the resources are orthogonal to each other.
Transmission resources might be frequency-domain resources, for example, frequency bands. FIG. 2 shows ICIC based on frequency domain, in which the entire frequency band F can be used in the central area of a cell while only a part of the entire frequency band (for example, F1, F2, or F3) can be used in the marginal area of the cell. Moreover, frequency band used in marginal areas of adjacent cells are different. Transmission resources may also be time-domain resources, for example, time segments. FIG. 3 shows ICIC based on time domain, in which the entire time segment T can be used in the central area of a cell while only a part of the entire time segment (for example, T1, T2, or T3) can be used in the marginal area of the cell. Moreover, time segments used in marginal areas of adjacent cells are different.
During specific implementation of ICIC in LTE, a specific power is generally set for a “dedicated channel” of a UE according to an area in which the UE is located. For example, in the ICIC based on frequency domain, a specific power is set for a Physical Downlink Shared Channel (PDSCH) allocated to a UE to bear UE dedicated data in a specific frequency band; in the ICIC based on time domain, specific powers are set for a Physical Downlink Control Channel (PDCCH) and a PDSCH allocated to a UE to bear UE dedicated scheduling information and UE dedicated data in a specific time segment respectively. The specific setting is mainly to improve the power of marginal transmission resources and reduce the power of central transmission resources. However, no specific power is set for a common channel or common signal of all UEs in a cell, such as a Physical Broadcasting Channel (PBCH), a Physical Control Format Indicator Channel (PCFICH), a Physical Hybrid ARQ Indicator Channel (PHICH), a common PDCCH bearing scheduling information on a Broadcasting Channel (BCH) and a Paging Channel (PCH), a common PDSCH bearing data on a BCH and a PCH, and a CRS), that is, a reference power is adopted. The Energy per Resource Element (EPRE) of the CRS is generally a cell-level fixed value configured by a background network manager through network planning and network optimization, that is, the transmitting power of each Resource Element (RE) of the CRS is fixed and same by default.
However, the CRS would produce co-channel interference on other channels in a neighbour cell and which are on the same symbol with the CRS, such as a PDCCH and a PDSCH, this is because the CRS of a cell is generally staggered from that of a neighbour cell in frequency domain and no interference is generated between the CRSs. As shown in FIG. 4, each small square represents one RE, square T01 represents the RE of the CRS of cell 1, square T02 represents the RE of the CRS of cell 2, square D represents the RE of data, cell 1 and cell 2 are adjacent to each other, and the RE frequency domain position of the CRS of cell 1 is staggered from that of the CRS of cell 2. However, such configuration causes the CRS to conflict in frequency domain with a PDCCH, a PCFICH, a PHICH, a PDSCH or the like in a neighbour cell which is in the same symbol with the CRS, thereby producing co-channel interference. Since the CRS is continuously transmitted in time domain, frequency domain and spatial domain, interference impact does not allow to be ignored; particularly for a UE in the marginal area of a cell, interference is significant. According to theoretical analysis, system simulation and actual tests, even if in the condition of only one neighbour cell of no load, downlink throughput of a PDSCH for a UE in the marginal area of a cell would be reduced by half due to the interference of a CRS of a neighbour cell, and during inter-cell handover, the throughput is reduced more.